Synchronization in multiplex signaling



May 15, 1928.

1,669,450 5. BRAND SYNCHRONIZATION IN MULTIPLEX SIGNALING Filed May 1926 2'Sheets-Sheet 1 IN VENTOR v Smart firm/mt May 15, 1928. 1,669,450

8. BRAND SYNCHRONIZATION IN MULTIPLEX SIGNALING Filed May 1. 1926 2 Sheets-Sheet 2 11V VENTOR Smart firm ed A TTORNE y Patented May 15, 1928.

U I E STATES snAR'r EBBAND, or BnooKLYN, YORK,

TELEGRAPH COMPANY, A o

A J I NQMQ AMEB CAMELE HQ EAND ORPYORATION or NEW Yonk. P

synonnonize'rron IN MULTIPLEX sterner-line.

Application filed May 1,

It is an object of my invention to provide a method and suitable apparatus for estab' lishing and maintaining proper synchronis'm and phase relations in a multiplex carrier current signaling system. .In a system in which, at the receiving end, there are locally generated currentseach of the same fre quency as respective received carrier current components, it is an object of my invention to establish and maintain synchronism and proper phase relation between each received carrier current component and the respective locally generated current of the same frequency. These objects of my invention, and other objects will become apparenton consideration of an example of procedurein accordance with the invention which Iha-ve chosen to disclose in this specification taken with the accompanying drawings. It will be understood that this specification relates largely to this particular example of the invention, and that the invention will be defined in the appended claims.

Referringto the drawings Figu-re 1.is a diagram of transmittingapparatusthat may be employed in practicing my invention. Fig. 2 is adiagramof corresponding receiving apparatus, and Fig. 3 is a diagram illustrating certain phase relations that will be referred to in explaining the principle involved in the operation of the system of Figs. 1 and 2.

At the sending end shownin Fig. 1, the generator 2 1 delivers an alternating current of a certain fundamental trequencyto the harmonic generator .2 which may. be arranged so that its outputwill comprise the said fundamental and odd harmonics thereof. For example, the fundamental "frequency may he cycles per second, and the odd harmonics would accordingly have frequenci-es of 85+170, 85 +840, etc.

The superposed harmonic currents from theharmonic generator--22 go to the bus-bars 23 and thence, respectively, through the multiplehand filters 24, each adapted to pass one and only one of the said harmonic cur- .rents. The current through one such band filter 24 goes unmodified to the bus-bars 29 an d'thence to the line L. This current is tor .synchroni'zing at the receiving end, as will be explained presently. In connection with the numerical frequency values that have been suggested, thissynchronizing our- 1926. SerialgNo. 106,099.

rent may conveniently be taken at the frequency of 1275- cycles per second;

The current through each of the other band filters 24 goes to a phase splitter PS1) which delivers 1 two currents of the input frequency apart in phase over the respective conductor pairs 25 and 26. Thesetwo currents go over these conductor pairs to the sending network SN where each current com ponent is controlled by a corresponding key K, or ,K Each key operates when it is shifted to reverse the phase of the corresponding current component. 'These current components as controlled by the said keys are superposed in the conductors 27 leading to the band filter 28 through which they pass to the bus-bars 29 and the-line L.

At the receiving station shown in Fig. 2, these superposed current components of V214 rious frequencies, each comprising two components 90 apart,-eacl1 such'component hay- .ing its phase" reversed from time to time by signaling changes, all come in on the line L and go thence to the bus-bars 30. The respective frequency bands are separated and pass through the respective band filters '31 to thecorresponding receiving networks Bymeans presently to be described, the oscillation generator 33 generates a fundamental current of the same frequency asjor the generator 21 atthe sending end. This current goes fromthegenerator 33 to the harmonic generator 34 which may bemade sothat itsoutput'comprises the odd. liarmonics, all of which are put on the bus-bars These harmonics are separated. out and passed by therespectiveband filter 36, and from each such band filter 36 the correspond ing current of a single frequency goes through the adjustable phase shifter 37 to the phase splitter 38 whose output -consists of two currents of the same frequency,- 90 apart in phase,awhich go to the receiving networlrRlf'l or 32. v

Each .receiving network 32 controls two receiving relays such as 39 and 40., One relay 39"is affected by one componentfrom the line, and changesbetween markingand spac other component of currentfromthe line,

Current ofthe same local harmonic generator and it operates only on changes between the phaseagreementand phase opposition for the corresponding component ,ofmreceived current on the line and the locally generated current component.

These relays 39 and 40 control respective circuits 42 to signal receiving polarizedrelays 43. Normally, the multiple double throw switch S is thrown to the right so that one armature position for sucha relay as 39 or 40 puts positive battery 41 on the line 42, and the other armature position puts negative battery 44 on the line- 42.

i The particular frequency, appropriated. for synchronizing that goes through the band filter 24"at the sending end is received through the band filter '51 at the receiving end and goes toafl'ect alike the grids of the two detectors 49 and 5 0.

frequency from the 34 is passed through the band filter 47 and applied through the transformer 148 to affect oppositely the grids of the two detectors 49 and 50. i w

TVhen t-he two input electromotive forces from the respective filters 51 and 47 are 90 apart, the effect in the plate circuit relay52 will be neutral, but any departure from the 90 relation will give an unbalanced effect in the plate circuit of the. detectors 49 and 50 and shift the arn'iature 52 one; way or the other, accordingly. i

' The oscillation generator 33 hasits usual tuned circuit comprising inductance and capacity, the normal capacity being represented by the condenser 53; This capacity is slightly less than the proper magnitude to putt-he oscillator 33 in synchronism with the generator 21 at the sending station.) Ac

cordingly, when the contactscontrolled by,

the relay 52 are open, the oscillator 33 tends "to speed up a little and causes ,adepartmre 45 from the 90 relation between the'input electromotive forces for theldetectors 49 and 50.

\Vhenthe departure from the, 90 relation becomes great enough, it causes the contacts of the relay 52 to close, thus putting thecondenser 54 in parallel with the condenser 53 and slightly increasing the capacity of the tuned circuit of the oscillator 33. This in- 1 crease of capacity is enough to make the oscillator slightly too slow. Accordingly, the oscillator slows down a little until. the 90 reaction is restored for the inputelectromotive forces on the detectors49 and 50, whereupon the/contacts of rela 52 0 en again. Thus it willbe seen that t e osci la-.

tor 33 is held closely at the same frequency, with the sending generator 21 and indefinite phaseirelation therewith.

It has already beenstated that the normal conditionof the switch. S isthrown to the.

right. It will be seen that from certain of the receiving network, relays such as and 5B,the conductors 45"to the signal relays 46 lead through respective arms of this switch Sq v v H i Whenthe system is tobestarted up, it is necessary to have properphase relation be tween each; one of the received current com ponents through. respective filters such as 31,

'andeach one of the locally generated current components taken off through respective filters such as 36. It will be seen that synchronism and phase agreementbetween the .particular Zcurrent components through the band filters 47 and 51 does not insure phase agree ment for the other components nor for the fundamental of ,all the components, It is true that such phase agreementmight be secured by adjustment ofthe various phase shifters 37, but .on starting up the system after a shutdown, it would be a tedious matter to adjust all: these phase shifters. By my invention, it becomes possible, when starting up the. system'after a shut down,

\quickly to secure the desired synchronism" Fig. 2. The numeral part, use or 7, means the'harlnonic for the corresponding relaynas the fifth or seventh, and the letters A andB distinguish the two phases 9Q apart.

To establish operation at propersynchronism and phase, relation, the switch S is thrown, over to theleft, thus disconnecting certain of the signalindicating relays 46 and connecting in multipletofthe jrelay TO all the conductors 45 from'the armature contacts of relays 5A, 5B, 7A, 7B, 9A and 9B.

By routine arrangement, the sending keys for both phases of the fifth, seventhand ninth harmonics are held closed atmarking position. The switch S being thrown to the left takes battery 44 off the nnirking contacts of the relays 5A,, 5B, etc., and connects buzzer 7.3 to an miniature-contact controlled ,byrelay 70. As will be shownpresently, therelays 5A, 513, etc, will not all mark even though the corresponding keysat the sending end' are held at marking, unless the phase relations are correct for all the com ponents of the system; but when the phase relations are correct, these relays will alll mark, provided the correspondingkeys are "held at marking. Assuming that these phase; relations arenot correct, then at least one of thearmatures of the relays 5A ,5B, etc., will be on itsupper; or spacingcon' tact, thus putting battery 41 on some h conductor as 45- ,and thence through the sWitchS to thevrelay 7O. There layZO, being energized,;will cut off the batterylfl,from the plate circuit of the detectors 49 and 50,

tively to the oscillator 21 at the sending end.

The diagram of Fig. 3 represents one complete cycle of phase shiftbetween these two oscillators. At the zero position, they are sup iosed to be in the proper phase relation with all their harmonics in proper phase relation. At this zero position of relative phase shift between the generators of the current of fundamental frequency, all the receiving relays will be marking for which the corresponding sending keys are held inmarking position. As the phase between the two generators shifts, the various relays will mark and space alternately. In one cycle of phase shift between the two generators, the relays on the fifth harmonic will mark and space five times, as represented by the horizontal line segments in the upper part of Fig, 3. That is, as the relative phase shift between the fundamentals progresses from zero, we read the diagram of Fig. 3 fromv left to right, and the top row of horizontal line segments showsby the lines when the relay 5A is marking, and by the intervening spaces when the said relay is s )acing. For example, at four-fifteenths of a cycle of relative phase shift the relay is spacing, but just before iive-fifteenths of a cycle of relative phase shift, the relay- It is assumed that each 5A begins to mark. relay marks half the time and spaces half the time. It may be sufficient if this condition is satisfied only approximately. It is a condition that may be secured by adjustment of the relays.

Similarly, for one cycle of relative phase shift between the fundamentals the relays 7A and 713 each mark and space seven times, and the relays 9A and 913 each mark and space nine times.

An inspection of Fig. 3 shows that only at zero relative phase shift are all the relays marking at the same time. at live-fifteenths of a complete cycle of rela-v tive phase shift, relays 5A, 7B, 9A and 9B are marking, but 513 and 7A are spacing.

Accordingly, for any position of relative phase shift of the fundamentals except the zero position, someone at least of the relays 5A, 513, etc, will be spacing, and the corresponding armature will be on its upper contact, thus holding battery ll on relay 70. But when the relative phase shift has proceeded to the stage of a cycle corresponding to the abscissa in Fig. 3, and all the relays 5r 513. etc. are marking, this opens the circuit from battery ll to relay which accordingly drops its armatures, thus removing the condenser 55 from the tuning For example,

paratus keeps in synchronism. The opera tron of the buzzer notifies the attendant that the proper phase relation forthe oscillator iij has been reached, and he throws the switch 8; from left-to right, thus connecting negative battery si lto the marking contacts of the relays 39, 40, 5A, 5B, etc,-

and cutting off the buzzer 73 from battery '71. This leaves the system subjectto normal control through the detectors 49 and 50,

which serve to hold the oscillator 33 in the proper phase relation, as heretofore dc SCX'llJGCl. I By throwing the switch S from the position shown in Fig. 2, the switch S can be made to operate automatically. It will be.

seen that in this case instead of operating .the buzzer 78, the magnet 74 isoperated,

which withdraws v the dog 75 holding the end of the switch arm 76, and this permits the spring 77 to throw the switch arm 76.

to the right. I claim: 1. The method of bringing. a set of harmonic currents respectively into synchronisnrwith another set of such currents, which consists in causing a slowly increasing relative .lagbetween the two sets of currents until a suiiicie-nt number of components oi the two sets of currents are in phase and then initiating automatic regulation of one set of currents to hold them in phase with the currents of the other set by applying one current of one set to regulate the corresponding current of the other set.

2. The method of establishing phase agreement between each of a set of locally generated harmonic currents and each'of a corresponding set of received harmonic currents, which consists in slowly shifting the phase of the locally generated currents relatively to the received currents until there is phase agreement between enough of the currents of the two sets respectively to necessitate phase agreement throughout, and then applying one of the received currents to regulate the corresponding locally gen erated current.

3. The method of initiating automatic' then starting the automatic synchronizing apparatus in operation.

4. The method of bringing two sets of eating phase agreement and phase opposi-.j

harmonic alternating currents into respec tive phase agreement, which Consists in indition for each pair'of currents of thetwo sets and permitting a drift'in phase between the two sets until phase'agreenient is 111- dicated by a selected number of the pairs: of: currents SLllllClEZIlt to determine phase agreement throughout, and then initiating synchronous control of one set wlth the other by automatic interaction between a particular current of one set and the corresponding current of the other set. p

"In combination, in a multiplex"carrier current receiviiig systemin which the re ceived currents areharmonics of one fundamental, local means to generate harmonic currents corresponding approXimate-ly in frequency with the respective received currents, respective relays each operated accordingto thephase agreement of a received current and thecorresponding locally tion of enough of the relays to determine generated current, regulating means and means to lnltlflte operation of said regulatmg means responsive to simultaneous operaphase agreement for all the currents.

6. In combination, in a multiplex carrier current receiving system in which the received currentsare harmonics of one fundamental, local means to generate harmonic currents corresponding approximately in frequency with therespective received currents, respective relays each' operated by conjoint action of a received current and the corresponding locally generated current,

synchronizing means and meansto initiate its act on responsive to the slmultaneous operation of enough of the relaysto deter mine phase agreement forall the currents.

7;. In combination, in a'niultiplex carrier current receiving system in which the received currents are harmonics of one fundamental, local means to generate harmonic currents corresponding approximately in frequency with the respective received currents, synchronizingmeans, and means to initiate the operation thereof, said last- 111011 tioned means controlled by the con oint acdamental, local means to generate a set of harmonic currents corresponding approximately to said received currents, a regulator for maintaining synchronismainong all the currents respectively when once it established, respective means responsive accordingto thephase relation ofthe various currents and means operated thereby to indie [cate when the synchronizing apparatus should be started in operation. 7

In testimony whereof, I have signed my April 1926. L

' SMART BRAND,

'name to this specification this 29th day of 

